Field
Embodiments of the invention are related to inspecting a photo resist film material layer, such as formed on the top surface of a conductive layer of a chip package, to detect border defects between regions of light exposed (e.g., cured) and unexposed (e.g., uncured) resist film material.
Description of Related Art
One of the key issues resulting in high yield loss in substrate package technology development (SPTD) or bump-less build-up layer (BBUL) packaging is unacceptable borders or defective borders (e.g., “border defects”) between regions of light exposed (e.g., cured) and unexposed (e.g., uncured) resist film material.
Currently no solutions exist in the industry for 3-Dimensional (3D) imaging and quantitative characterization of photo-resist during or after exposure to light to cure the material, such as to identify border defects. This greatly limits process development and optimization for substrate technology development. Inconsistencies or defects in the exposure lighting, or mask used to expose the exposed regions may be contributors for border defects “hidden defects”. Such defects can include dry film resist (DFR) border defects of film patterned onto electroless conductor (e.g., copper) to form conductive traces (e.g., copper traces) on an insulating layer or on a package substrate.
Such defects can result in inaccurate or unacceptable trace geometry, and thus cause conductive traces to malfunction, short to other traces, or open circuit where contact should exist. Such defects also can result in smaller contact area between conductive traces and insulating substrate, and thus cause conductive trace to lift off in downstream process. Such liftoff can result in damaged, destroyed or missing lengths of the conductive traces, often causing undesired open circuits in the trace circuitry.
Therefore, it is desirable to provide imaging and quantitative characterization of photo-resist during or after exposure to light to cure the material, such as to identify border defects.